Epoxidized diene elastomers for exterior block crosslinking

ABSTRACT

An epoxidized diene block polymer comprising at least interior and exterior diene blocks wherein the exterior diene blocks contain a greater concentration of di-, tri- and tetrasubstituted olefinic epoxides than the interior blocks and wherein the exterior blocks contain from 0.2 to 10 Meq of olefinic epoxides per gram of exterior blocks and the molecular weights of the exterior blocks are from 3000 to 50,000 and the molecular weights of the interior blocks are from 15,000 to 200,000.

This is a division, of application Ser. No. 07/863,579, filed Apr. 3,1992.

BACKGROUND OF THE INVENTION

This invention relates to epoxidized diene block elastomers suitable forendblock crosslinking and adhesive compositions made therefrom.

Curing of adhesives based on conjugated diolefins and, optionally, vinylaromatics has increased the range of service properties for suchadhesives. Radiation curing and chemical curing of polymers to make suchadhesives is known. This curing causes covalent crosslinking of thepolymerized conjugated diolefins which is evidenced by a high gelcontent of the crosslinked polymer. Before crosslinking, the polymersare melt processable but after crosslinking, the gel cannot be processedas melts. Crosslinking therefore enhances solvent resistance andimproves elevated temperature shear properties. Compositions cantherefore be applied to a substrate in a melt and then crosslinked toform a superior adhesive. However, improvements in the adhesives couldbe made if the adhesives could be cured at lower dosages of radiation,provide longer term heat resistance, or provide improved weatherability.

Further, the known curable adhesives which are based on vinyl aromaticsand conjugated diolefins do not have particularly good long term heat,weather and ultraviolet stability due to the need to utilizeunhydrogenated polymers. The known-vinyl aromatic-conjugated diolefinbased adhesives which are curable are unhydrogenated polymers.Hydrogenation is known to improve long term heat, weather andultraviolet stability, but it removes the double bonds which are neededto effect the curing by radiation crosslinking. Such curing methods arenot effective when the polymers are hydrogenated. The requirement forthis unsaturation is particularly evident when typical tackifiers arepresent in the compositions because their presence generally inhibitscrosslinking of the polymer.

It is an object of the present invention to provide an epoxidizedcopolymer which may be crosslinked, preferably by radiation, which ismelt processable before crosslinking but has a high gel content aftercrosslinking. Further, it is an object of this invention to provide anadhesive composition which is based on this crosslinkable blockcopolymer.

SUMMARY OF THE INVENTION

The present invention comprises elastomeric block copolymers, based onat least one conjugated diolefin monomer, that contain a greaterconcentration of di-, or tri-, or tetrasubstituted olefinic epoxides inthe exterior blocks, and lesser concentration in the interior blocks ofthe polymer. The polymers of the invention may or may not behydrogenated and if they are hydrogenated, the hydrogenation may takeplace either before or after epoxidation. The polymers may becrosslinked through at least some of the epoxy functionality, preferablyby radiation, and can be used to make rapid curing and heat stableadhesives, sealants, coatings, used as additives to modify asphalt,flexible printing plates, fibers, and films, and also as modifiers forpolyesters and polyamides.

The exterior A blocks.contain a greater concentration of di-, tri-, ortetrasubstituted olefinic epoxides (1,1-disubstituted,1,2-disubstituted, 1,1,2-trisubstituted, and 1,1,2,2-tetrasubstitutedolefinic epoxides) than the interior B blocks. The A blocks contain suchepoxides within the concentration range of 0.2 to 10 milliequivalents(Meq) per gram of block A, preferably within the range of 0.5 to 8Meq/g, and most preferably within the range of 1 to 5 Meq/g. Preferably,the ratio of the concentration (Meq/g) of such epoxide groups bonds in Ato the concentration in B should be at least 3:1, more preferably, theratio should be greater than 5:1.

The molecular weight of the A blocks is above 3,000 and not higher than50,000, preferably between 3,000 and 25,000, most preferably between3,000 and 15,000. The molecular weight of the B blocks is above 15,000and not greater than 200,000, preferably between 15,000 and 100,000,most preferably between 15,000 and 50,000.

DETAILED DESCRIPTION OF THE INVENTION

The general methods of making block copolymers are reviewed by R. P.Quirk and J. Kim, "Recent Advances in Thermoplastic ElastomerSynthesis," Rubber Chemistry and Technology, volume 64 No. 3 (1991),which is incorporated herein by reference. Especially useful is themethod of sequential anionic polymerization of monomers. The types ofmonomers that will undergo living polymerization are relatively limitedfor the anionic method, with the most favorable being conjugateddiolefins and monoalkenyl aromatic hydrocarbon monomers. Generally, ahydrogenation step is needed to prepare a saturated polymer. Hence, apolymer of this invention that is both epoxidized and saturated usuallyrequires both an epoxidation and a hydrogenation step. However, polymersmade by sequential polymerization of a suitable diolefin monomer and amonomer having only one carbon-carbon double bond or by sequentialpolymerization of two different mixtures (ratios) of such monomers,using either a monofunctional initiator, a monofunctional initiator anda coupling agent, or a multifunctional initiator, may be epoxidized andwould not have to be hydrogenated to produce an epoxidized polymer ofthis invention that is saturated.

The polymers containing olefinic unsaturation or both aromatic andolefinic unsaturation may be prepared using anionic initiators orpolymerization catalysts. Such polymers may be prepared using bulk,solution or emulsion techniques. Polymers prepared in solution arepreferred for subsequent epoxidation and hydrogenation.

A very useful embodiment of this invention may be conveniently preparedby anionic polymerization, preparing blocks A and B, (optionally M andC, discussed below), each consisting of homopolymers or copolymers ofconjugated diene monomers or copolymers of conjugated diene monomers andalkyl aryl monomers wherein the monomers used for the A blocks are suchthat the A blocks have a greater average number of highly substitutedresidual olefinic double bonds per unit of block mass than do the Bblocks. Since the desired final polymer is to be elastomeric, it isnecessary that the amount of the alkyl aryl monomers in the interior Bblocks does not exceed 50% by weight. The amount of alkyl aryl monomerscopolymerized in the A blocks can be greater, up to 99%, provided thatenough conjugated diene monomer is used to assure the presence of asufficient level of higher substituted olefinic double bonds in A forepoxidation.

The polymer is epoxidized under conditions that enhance the epoxidationof the more highly substituted olefinic double bonds, such as by the useof peracetic acid, wherein the rate of epoxidation is generally greaterthe greater the degree of substitution of the olefinic double bond (rateof epoxidation:tetrasubstituted>trisubstituted>disubstituted>monosubstituted olefinicdouble bond). Sufficient epoxidation is done to achieve the desiredlevel of epoxidation in the A blocks (within the range of 0.2 to 10Meq/g). ¹ H NMR can be used to determine the loss of each type of doublebond and the appearance of epoxide.

If a substantially saturated polymer is desired, the epoxidized polymeris hydrogenated to remove substantially all remaining olefinic doublebonds (ODB) and normally leaving substantially all of the aromaticdouble bonds. If only substantially saturated interior blocks aredesired, the epoxidized polymer may be partially hydrogenated in aselective manner with a suitable catalyst and conditions (like those inRe. 27,145, U.S. Pat. No. 4,001,199 or with a titanium catalyst such asis disclosed in U.S. Pat. No. 5,039,755, all of which are incorporatedby reference; or by fixed bed hydrogenation) that favor thehydrogenation of the less substituted olefinic double bonds (rate orhydrogenation:monosubstituted>disubstituted>trisubstituted>tetrasubstituted olefinicdouble bonds) and also leaves aromatic double bonds intact, so as tosaturate the B blocks and leave some or all of the unsaturationintact.in the A blocks and/or any portions of the optional M block orthe C arms that may also contain unepoxidized higher substitutedolefinic double bonds.

Alternatively, selective partial hydrogenation of the polymer may becarried out before epoxidation such that between 0.2 and 11.6 Meq ofolefinic double bonds are left intact, as required of an A block forsubsequent epoxidation. Fully epoxidizing 11.6 Meq of ODB per gram ofpolymer gives 10.0 Meq of epoxide per gram of the final polymer becauseof a 16% weight gain due to the added oxygen. If selective partialhydrogenation is done first, the epoxidation does not need to beselective with respect to the degree of substitution on the olefinicdouble bonds, since the objective is usually to epoxidize as many of theremaining ODB's as possible. After hydrogenation, it is preferred thatthe ratio of ODB's in the A blocks to that in the B blocks be at least3:1.

Generally, if a hydrogenation step is used, sufficient improvement ofthe polymer's chemical and heat stability should be achieved to justifythe extra expense and effort involved, and this generally means at leastsaturating the interior blocks B to the point that they have less than 1Meq of olefinic double bonds per gram of B left intact. For greatestheat stability, all of the olefinic double bonds, anyplace in thepolymer, that are not epoxidized should be removed so that less than 1Meq of ODB per gram of polymer remain, more preferably less than 0.6Meq/g, and most preferably less than about 0.3 Meq/g of polymer.

In general, when solution anionic techniques are used, conjugateddiolefin polymers and copolymers of conjugated diolefins and alkenylaromatic hydrocarbons are prepared by contacting the monomer or monomersto be polymerized simultaneously or sequentially with an anionicpolymerization initiator such as group IA metals, their alkyls, amides,silanolates, napthalides, biphenyls and anthracenyl derivatives. It ispreferred to use an organo alkali metal (such as sodium or potassium)compound in a suitable solvent at a temperature within the range fromabout -150° C. to about 300° C., preferably at a temperature within therange from about 0° C. to about 100° C. Particularly effective anionicpolymerization initiators are organo lithium compounds having thegeneral formula:

    RLi.sub.n

wherein R is an aliphatic, cycloaliphatic, aromatic or alkyl-substitutedaromatic hydrocarbon radical having from 1 to about 20 carbon atoms andn is an integer of 1 to 4.

Conjugated diolefins which may be polymerized anionically include thoseconjugated diolefins containing from about 4 to about 24 carbon atomssuch as 1,3-butadiene, isoprene, piperylene, methylpentadiene,phenylbutadiene, 3,4-dimethyl-1,3-hexadiene, 4,5-diethyl-1,3-octadieneand the like. Isoprene and butadiene are the preferred conjugated dienemonomers for use in the present invention because of their low cost andready availability. The conjugated diolefins which may be used in thepresent invention include isoprene (2-methyl-1,3-butadiene),2-ethyl-1,3-butadiene, 2-propyl-1,3-butadiene, 2-butyl-1,3-butadiene,2-pentyl-1,3-butadiene (2-amyl-1,3-butadiene), 2-hexyl-1,3-butadiene,2-heptyl-1,3-butadiene, 2-octyl-1,3-butadiene, 2-nonyl-1,3-butadiene,2-decyl-1,3-butadiene, 2-dodecyl-1,3-butadiene,2-tetradecyl-1,3-butadiene, 2-hexadecyl-1,3-butadiene,2-isoamyl-1,3-butadiene, 2-phenyl-1,3-butadiene,2-methyl-1,3-pentadiene, 2-methyl-1,3-hexadiene,2-methyl-1,3-heptadiene, 2-methyl-1,3-octadiene,2-methyl-6-methylene-2,7-octadiene (myrcene), 2-methyl-1,3-nonyldiene,2-methyl-1,3decyldiene, and 2-methyl-1,3-dodecyldiene, as well as the2-ethyl, 2-propyl, 2-butyl, 2-pentyl, 2-hexyl, 2-heptyl, 2-octyl,2-nonyl, 2-decyl, 2-dodecyl, 2-tetradecyl, 2-hexadecyl, 2-isoamyl and2-phenyl versions of all of these dienes. Also included are1,3-butadiene, piperylene, 4,5-diethyl-1,3-octadiene and the like.Di-substituted conjugated diolefins which may be used include2,3-dialkyl-substituted conjugated diolefins such as2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-pentadiene,2,3-dimethyl-1,3-hexadiene, 2,3-diethyl-1,3-heoptadiene,2,3-dimethyl-1,3-octadiene and the like and 2,3-fluoro-substitutedconjugated diolefins such as 2,3-difluoro-1,3-butadiene,2,3-difluoro-1,3-pentadiene, 2,3-difluoro-1,3-hexadiene,2,3-difluoro-1,3-heptadiene, 2,3-fluoro-1,3-octadiene and the like.Alkenyl aromatic hydrocarbons which may be copolymerized include vinylaryl compounds such as styrene, various alkyl-substituted styrenes,alkoxy-substituted styrenes, vinyl napthalene, alkyl-substituted vinylnapthalenes and the like.

Conjugated dienes can also be copolymerized with methacrylates, such ast-butyl methacrylate, as described in U.S. Pat. No. 5,002,676, which isincorporated herein by reference, and such copolymers can be epoxidizedand hydrogenated as described herein. The preferred use position in thepolymer for methacrylates, when used, is in the C arms.

There are a wide variety of coupling agents or initiators that can beemployed. Any polyfunctional coupling agent which contains at least tworeactive sites can be employed. Examples of the types of compounds whichcan be used include the polyepoxides, polyisocyanates, polyimines,polyaldehydes, polyketones, polyanhydrides, polyesters, polyhalides, andthe like. These compounds can contain two or more types of functionalgroups such as the combination of epoxy and aldehyde groups, isocyanateand halide groups, and the like. Many suitable types of thesepolyfunctional compounds have been described in U.S. Pat. Nos.3,595,941; 3,468,972; 3,135,716; 3,078,254; 4,096,203 and 3,594,452which are herein incorporated by reference. When the coupling agent hastwo reactive sites such as dibromoethane, the polymer will have a linearA-B-A structure. When the coupling agent has three or more reactivesites, such as silicon tetrachloride, the polymer will have a branchedstructure, such as (A-B)_(n) -X. Coupling monomers are coupling agentswhere several monomer units are necessary for every chain end to becoupled. Divinylbenzene is the most commonly used coupling monomer andresults in star polymers.

In general, any of the solvents known in the prior art to be useful inthe preparation of such polymers may be used. Suitable solvents, then,including straight- and branched chain hydrocarbons such as pentane,hexane, heptane, octane and the like, as well as, alkyl-substitutedderivatives thereof; cycloaliphatic hydrocarbons such as cyclopentane,cyclohexane, cycloheptane and the like, as well as alkyl-substitutedderivatives thereof; aromatic and alkyl-substituted derivatives thereof;aromatic and alkyl-substituted aromatic hydrocarbons such as benzene,napthalene, toluene, xylene and the like; hydrogenated aromatichydrocarbons such as tetraline, decalin and the like; linear and cyclicethers such as methyl ether, methylethyl ether, diethyl ether,tetrahydrofuran and the like.

More specifically, the polymers of the present invention are made by theanionic polymerization of conjugated diene monomers and alkenyl aromatichydrocarbon monomers in a hydrocarbon solvent at a temperature between0° and 100° C. using an alkyt lithium initiator. The living polymerchains are usually coupled by addition of divinyl monomer to form a starpolymer. Addition monomers may or may not be added to grow more arms, Carms, or to terminally functionalize, such as with ethylene oxide orcarbon dioxide to give hydroxyl or carboxyl groups, respectively, andthe polymer and the living chain ends are quenched with a proton sourcesuch as methanol or hydrogen. Polymerization may also be initiated frommonomers such as m-divinylbenzene and m-diisopropenylbenzene treatedwith butyl lithium.

The block copolymers can be either linear polymers of the basic formula,A-B-A, and its simple variations, (A-B)_(k) and A-(B-A)_(j), orsymmetric and asymmetric star (centrally branched) polymers of the basicformula (A-B-M_(p))_(n) -X-C_(r), and its simple variations, ((A-B)_(j)-M_(p))_(n) -X-C_(r) and (A-(B-A)_(j) -M_(p))_(n) -X-C_(r), wherein A isthe exterior block, B is the interior block, M is an optional miniblock,and C is an optional arm (branch) consisting of one or more blocks. TheA-B-M_(p) arms (branches) and their simple variations are referred to asD arms when it is convenient to do so. The blocks themselves may behomopolymer or copolymer blocks including tapered blocks. The starstructures are preferred over the linear structures. Also preferred arenonrepetitive A-B diblock segments (where there is no subscript j in theformula).

M is a miniblock of monomer that can be used to affect the number orstability of the arms coupled or originating at X. The molecular weightof M is greater than 50 and less than 3000, preferably less than 1000. Mis a vinyl aromatic hydrocarbon or a diene, typically oligostyrene oroligoisoprene. For instance, when coupling anionically prepared A-B⁻⁻living arms, where A is polyisoprene and B is polybutadiene, withcommercial DVB-55 the degree of coupling to make the star is often lessthan 80%, with greater than 20% of the arms remaining unattached to themain star mode in the final product. The exact amount left unattached isvery dependent upon the exact conditions of the coupling reaction, suchas the amount of ether cosolvent used, the time elapsed afterpolymerization of the A-B arms and the temperature of the polymersolution during the DVB-55 addition. In contrast, when a small miniblockof oligoisoprene is incorporated to make the A-B-M arm, the couplingreaction is less sensitive to reaction conditions and degrees ofcoupling above 80 or 90% are typically achieved. Further, presence ofthe miniblock can be additionally beneficial when the polymer is beingused under harsh service conditions, such as high temperature use,because a completely saturated block like oligostyrene or an epoxidizedoligoisoprene can prevent scission of the arm from the star at the coreof the star.

X sits at the junction point or region in the polymer molecule at whichthe arms (branches) of the polymer connect and represents the agent oragents that function as the connector. Generally X either representscoupling agents or monomers that cause the majority of the arms to jointogether after polymerization of the arms, or represents an initiatorwith an active functionality of 3 or greater from which polymerizationof the arms takes place.

Asymmetric star polymers, by definition, require the use of the optionalC arms, which are necessarily different than the D arms. C arms areblock or multiblock segments that are usually prepared from one or moreof the monomers used to prepare the D .arms. The molecular weight of a Carm is between about 50 and 100,000, preferably between about 500 and50,000. The linear size of arms of greater length gives polymers withextremely high hot melt application viscosities. Care must be exercisedthat the combination C monomer selection, number of C arms or volumefraction of the C arms in the polymer does not change the overall natureof the polymer from one that is essentially elastomeric and primarilyepoxidized (and curable) in exterior blocks to one that is notelastomeric. Sometimes it is useful to prepare C from monomers otherthan those used in A or B. For instance, a methacrylate monomer, such ast-butyl methacrylate, can be added to a DVB-coupled star prior totermination and the arms C can be grown out from the living DVB core ofthe star.

The subscripts are integers that indicate how many times a particularblock or arm is present on a particular polymer. The subscript p is 0 or1, n and r are integers where n ≧2, r≧0, and n+r is the total number ofarms and ranges from 3 to 100, preferably from 5 to 50, and mostpreferably from 10 to 40. When p equals 0 or r equals 0 there is nominiblock M or no C arms. Preferably n≧r, and most preferably r=0.

The subscript k is 2 to 6 and j is an integer from 1 to 6. Larger valuesof j produce polymers that have very large linear size which yieldspolymers with extremely high hot melt application viscosities. Even whenthe subscript j is only in the range of 2 to 6, it is important that themolecular weights of the A and especially the B blocks are near thelower end of permissible values.

The total number of arms, n+r, and range from 3 to about 100, preferablyfrom about 10 to 40. As the number of arms increases, so does theaverage molecular weight of the polymer, which substantially increasesthe polymers ability to cure easily, such as with very low doseradiation, because the number of cure sites (epoxide sites) increases inproportion to the molecular weight at any fixed concentration of epoxidein the polymer. Fortunately, the substantially increased polymer toolecul ar weight causes very little increase in melt viscosity because ofthe compact nature of a star polymer. However, trying to attain thehighest possible number of arms on a star polymer often results in theformation of some gel during the manufacture of the polymer, which makessubsequent processing and filtering of the polymer during manufacture,light scattering analysis for molecular weight, or application of thepolymer difficult or impossible. This is why the most preferred upperbound for the number of arms is 40.

A special case is where A is a polyisoprene block polymerized underconditions that yields primarily 1,4-polyisoprene, for which theresidual double bonds are trisubstituted, and B is a polybutadiene blockfor which all of the residual double bonds are mono- or disubstituted.Another special case is where the A block is a randompolyisoprene/polystyrene copolymer in which a majority of thepolyisoprene is 1,4-polyisoprene and the B block is polybutadiene.Either epoxidation alone, epoxidation first followed by hydrogenation,or partial hydrogenation of these polymers first followed byepoxidation, works extremely well. When B is polybutadiene, it often isconvenient to use a miniblock M where M is oligoisoprene oroligostyrene, when making star polymers. The polymer can be epoxidizedto provide a level of epoxidation between 0.2 to 10 milliequivalents ofepoxy per gram of A, while the B blocks will contain a lesser amount ofepoxidation than A.

Another special case is the sequential polymerization of a singleconjugated diene monomer under two sets of reaction conditions. Anexample is the anionic polymerization of 1,3-butadiene in cyclohexane toproduce primarily 1,4-polybutadiene followed by addition of amicrostructure modifier, such as an ether cosolvent, and polymerizationof high 1,2-polybutadiene, followed by coupling and selectiveepoxidation to give an A-B-A or an (A-B-M_(o))_(n) -X-C_(o) polymer ofthis invention. A is 1,4-polybutadiene with disubstituted double bondsand B is 1,2-polybutadiene which has only monosubstituted double bonds.The polymer can be subsequently hydrogenated to remove substantially allof the remaining olefinic double bonds if a saturated polymer withmaximum long term heat resistance is desired. Here again, partialhydrogenation can be practiced first. However, it is better to epoxidizefirst since it is easier to very selectively epoxidize the1,2-disubstituted double bonds of the 1,4-butadiene over themonosubstituted double bonds of the 1,2-polybutadiene than it is toselectively hydrogenate the 1,2-polybutadiene over the1,4-polybutadiene. Obviously, this principle can be applied to thepolymerization of other conjugated diene monomers, such as 1,3-isoprene,that can be polymerized to different microstructures which differ in thelevel of substitution about the double bonds by a deliberate change inreaction conditions.

The following are illustrative examples of polymers encompassed by theabove nomenclature. A linear triblock copolymer made by sequentialpolymerization of the A block monomer(s), the B block monomer(s), andthen the A block monomer(s) again is described as an A-B-A polymer. Thepolymer made using a diinitiator in which the B block monomer ispolymerized in two directions, followed by the A block monomer, is alsosimply described by the nomenclature A-B-A. Likewise, the polymer madeby coupling two A-B⁻ arms with a difunctional coupling agent to form thelinear molecule is an A-B-A polymer. Normally, no A-B-A polymer is anentirely pure triblock polymer. Each synthetic method leaves some degreeof an intermediate structure due to dieout or some diblock due toincomplete coupling. A (A-B-M_(o))₁₅ -X-C_(o) is a symmetric starpolymer having 15 arms all of which are A-B diblock arms. The zerosubscripts on M and C mean that these are not present. The present(A-B-M_(o))₁₅ -X-C_(o) nomenclature is equivalent to (A-B)₁₅ -X, anomenclature commonly used for a symmetric star polymer. Star polymersare normally made by a coupling reaction using divinyl monomer such asdivinylbenzene. Like any coupling reaction, it does not go to 100%completion and some diblock polymer (unattached arms) will be present.The value of n, which in the present example is 15, is determined afterthe polymer is made. The best way to assign the n values is to measurethe weight average molecular weight of the polymer by light scatteringas described below, including pure star and diblock components, subtractfrom it the portion of the mass due to the coupling monomer and thendivide this corrected weight average molecular weight by the molecularweight of the arm which is usually the peak molecular weight determinedby GPC as described below.

(A-B-M_(o))₁₅ -X-C₅ where C is identical to a B block, is anasymmetrical star block copolymer. Such a polymer can be convenientlymade by initiating with alkyl lithium .and polymerizing the A blocks andthen adding 33% more lithium to the reactor prior to adding the B blockmonomer. Living A-B and B blocks will result that can be coupled withthe appropriate agent such as DVB-55 (a divinyl benzene product fromDow). A statistical distribution of species will be made by this processand will have the average (A-B)₁₅ -X-B₅ composition. (A-B-M₁)₂₀ -X-C₂₀polymer is an asymmetrical star block copolymer prepared by coupling 20A-B-M triblocks with a small number of coupling monomers, such as DVB,and then adding the polymerizing C block monomer onto the active siteson X before quenching the living system with a proton source.

As stated above, the molecular weight of A is above 3,000 and no greaterthan 50,000, preferably between about 3,000 and about 25,000, and mostpreferably between 3,000 and 15,000. The molecular weight of B is aboveabout 15,000 and no greater than 200,000, preferably between about15,000 and about 100,000, and most preferably between 15,000 and 50,000.The reason for these ranges and preferred ranges are that lowermolecular weight blocks make the polymers more difficult to crosslink atlow dose of radiation, while higher molecular weight blocks make thepolymers very difficult to apply to a substrate by melt or other means.The most preferred ranges balance the crosslinking and applicationrequirements the best for a hot melt system.

Molecular weights of linear polymers or unassembled linear segments ofpolymers such as mono-, di-, triblock, and etc., arms of star polymersbefore coupling are conveniently measured by Gel PermeationChromatography (GPC), where the GPC system has been appropriatelycalibrated. Polymers of known molecular weight are used to calibrate andthese must be of the same molecular structure and chemical compositionas the unknown linear polymers or segments that are to be measured. Foranionically polymerized linear polymers, the polymer is essentiallymonodisperse and it is both convenient and adequately descriptive toreport the "peak" molecular weight of the narrow molecular weightdistribution observed. Measurement of the true molecular weight of thefinal coupled star polymer is not as straightforward or as easy to makeusing GPC. This is because the star shaped molecules do not separate andelute through the packed GPC columns in the same manner as do the linearpolymers used for the calibration, and, hence, the time of arrival at aUV or refractive index detector is not a good indicator of the molecularweight. A good method to use for a star polymer is to measure the weightaverage molecular weight by light scattering techniques. The sample isdissolved in a suitable solvent at a concentration less than 1.0 gram ofsample per 100 milliliters of solvent and filtered using a syringe andporous membrane filters of less than 0.5 microns pore size directly intothe light scattering cell. The light scattering measurements areperformed as a function of scattering angle and of polymer concentrationusing standard procedures. The differential refractive index (DRI) ofthe sample is measured at the same wavelength and in the same solventused for the light scattering. The following references are hereinincorporated by reference:

1. Modern Size-Exclusion Liquid Chromatography, M. W. Yau, J. J.Kirkland, D. D. Bly, John Wiley & Sons, New York, N.Y., 1979.

2. Light Scattering from Polymer Solutions, M. B. Huglin, ed., AcademicPress, New York, N.Y. 1972.

3. W. Kay and A. J. Havlik, Applied Optics, 12, 541 (1973).

4. M. L. McConnell, American Laboratory, 63, May, 1978. Uponepoxidation, the exterior A blocks have a greater concentration of suchdi-, tri-, and tetrasubstituted olefinic epoxide than the interior Bblocks. Specifically, the Meq of such epoxide per gram of the A blockswill be from 0.2 Meq/g to 10 Meq/g, preferably from 0.5 to 8 Meq/g andmost preferably 1 to 5 Meq/g. The ratio of the concentration of suchepoxide in the A blocks to that of the B blocks will be at least 3:1 andpreferably greater than 5:1. If there were greater epoxidation in the Aor B blocks, the polymers would over crosslink, have little elasticityand be unsuitable for the applications intended. The polymer may then becrosslinked through at least some of the epoxy functionality, preferablyby radiation.

Some advantages of relatively low levels of epoxidation are:

the manufacturing cost is lower because less epoxidizing agent is used;

can maintain the polymer as an elastic material because the crosslinkingwill not be dense;

the polymer will be more hydrophobic so water will be less of a problem;

the polymer can be formulated in conventional equipment; and

the polymer is less subject to undesirable post curing.

The epoxidized copolymers of this invention can be prepared by theepoxidation procedures as generally described or reviewed in theEncyclopedia of Chemical Technology 19, 3rd ed., 251-266 (1980), D. N.Schulz, S. R. Turner, and M. A. Golub, Rubber Chemistry and Technoloqy,5, 809 (1982), W-K. Huang, G-H. Hsuie, and W-H. Hou, Journal of PolymerScience, Part A: Polymer Chemistry, 26, 1867 (1988), and K. A.Jorgensen, Chemical Reviews, 89, 431 (1989), and Hermann, Fischer, andMarz, Angew. Chem. Int. Ed. Engl. 30 (No. 12), 1638 (1991), all of whichare incorporated by reference.

For instance, epoxidation of the base polymer can be effected byreaction with organic peracids which can be preformed or formed in situ.Suitable preformed peracids include peracetic and perbenzoic acids. Insitu formation may be accomplished by using hydrogen peroxide and a lowmolecular weight fatty acid such as formic acid. Alternatively, hydrogenperoxide in the presence of acetic acid or acetic anhydride and acationic exchange resin will form a peracid. The cationic exchange resincan optionally be replaced by a strong acid such as sulfuric acid orp-toluenesulfonic acid. The epoxidation reaction can be conducteddirectly in the polymerization cement (polymer solution in which thepolymer was polymerized) or, alternatively, the polymer can beredissolved in an inert solvent such as toluene, benzene, hexane,cyclohexane, methylenechloride and the like and epoxidation conducted inthis new solution or can be epoxidized neat. Epoxidation temperatures onthe order of 0° to 130° C. and reaction times from 0.1 to 72 hours maybe utilized. When employing hydrogen peroxide and acetic acid togetherwith a catalyst such as sulfuric acid, the product can be a mixture ofepoxide and hydroxy ester. The use of peroxide and formic acid in thepresence of a strong acid may result in diolefin polymer blockscontaining both epoxide and hydroxy ester groups. Due to these sidereactions caused by the presence of an acid and to gain the maximumselectivity with respect to different levels of substitution on theolefinic double bonds, it is preferable to carry out the epoxidation atthe lowest possible temperature and for the shortest time consistentwith the desired degree of epoxidation. Epoxidation may also beaccomplished by treatment of the polymer with hydroperoxides or oxygenin the presence of transition metals such as Mo, W, Cr, V and Ag, orwith methyltrioxorhenium/hydrogen peroxide with and without aminespresent. ¹ H NMR is an effective tool to determine which and how much ofeach type of ODB is epoxidized. Further, the amount of epoxy can also bemeasured by the direct titration with perchloric acid (0.1N) andquarternary ammonium halogenide (tetraethyl-ammonium bromide) where thesample is dissolved in methylene chloride. Epoxy titration is describedin Epoxy Resins Chemistry and Technoloqy, edited by Clayton A. May andpublished in 1988 (p. 1065) which is herein incorporated by reference.

An epoxidized polymer of the present invention can be furtherderivatized by a subsequent reaction either separately or in-situ toprovide useful reactive elastomeric binders that have reactivefunctionality other than the epoxy group. Epoxy groups can be convertedto hydroxyl functionality, capable of crosslinking withamino-formaldehyde resins or isocyanates, by reduction or reaction withwater. Reaction with azide ion, reaction with cyanotrimethylsilanefollowed by reduction or reaction with dialkylaminosilanes, ammonia, oramines will give polymers containing both amino and hydroxylfunctionality that can be used to enhance adhesion to cellulosicsubstrates or provide reactive sites for isocyanate cure. Reaction withamino or mercapto acids can be used to prepare polymers containinghydroxyl and carboxylic acid functionality, providing greater adhesionto metals or to basic polymers such as nylon. Reaction withmercaptosilanes can be used to prepare polymers containing the elementsof coupling agents, providing excellent adhesion to glass. Thesefunctional groups may also be introduced in the form of protectedfunctional groups by reaction of the epoxy with the appropriatelyfunctionalized organometallic reagent (lithium organocuprates, Grignardreagents). Hydroxyl and aldehyde functionality may also be introduced byhydroformulation. Reactions with acrylamides and acrylic acids willintroduce sites for free radical grafting. Further neutralization of thecarboxylic acid or amine-containing polymer with base or acid will givevarying amounts of water dispersability, depending on the level offunctionality and neutralization.

A partially hydrogenated, but not epoxidized, polymer of the presentinvention can be further derivatized as well. Such a polymer can behalogenated, for example, by reacting it with a solution of HBr inacetic acid, or with chlorine (Cl₂) or bromine (Br₂), either gaseous, orin solution. A wide variety of species, including alcohols, carboxylicacids and nitriles, can be added across the double bond in the presenceof protic acids to form the corresponding ethers, esters and amides.Acid chlorides and anhydrides can be added across the double bond in thepresence of Lewis acids. A wide variety of species containing activeprotons, including thiols, primary alcohols and amines, aldehydes andspecies of the structure ZCH₂ Z', where Z and Z' are electronwithdrawing groups, such as NO₂, CN, or CO₂ H, can be added across thedouble bond in the presence of radical generators, such as organicperoxides. Hydroboration can be used to prepare the alkylborane, asdescribed in S. Ramakrishnan, E. Berluche, and T. C. Chung,Macromolecules, 23, 378 (1990), and subsequent papers by T. C. Chung.The alkylborane derivative may then be transformed to the alcohol, oramine, or other functional groups. Diazo compounds may be added to thedouble bonds, either under the influence of heat, or metal catalysts,such as Cu and Rh salts. Reactive dienophiles, such as maleic anhydrideand di-t-butyl azodicarboxylate can be added to the double bond to formthe anhydride or the hydrazide (which can be thermally converted to thehydrazine), respectively. Reactive dipoles, such as nitrile oxides andnittones can be added to the double bond. Hydrogenation of the abovementioned derivatives can be used t0 introduce amino--alcoholfunctionality. A variety of oxidative reactions, including oxidationwith potassium permanganate and sodium perborate, may be used tointroduce hydroxyl groups.

The polymers of this invention are preferably cured (crosslinked}byultraviolet or electron beam radiation, but radiation curing utilizing awide variety of electromagnetic wavelengths is feasible. Either ionizingradiation such as alpha, beta, gamma, X-rays and high energy electronsor non-ionizing radiation such as ultraviolet, visible, infrared,microwave and radio frequency may be used. The details of radiationcuring are given in commonly assigned copending applications Ser. No.692,839, filed Apr. 28, 1991, "Viscous Conjugated Diene BlockCopolymers" and Ser. No. 772,172, filed Oct. 7, 1991, "Crosslinked EpoxyFunctionalized Block Polymers and Adhesives," both of which are hereinincorporated by reference.

Reactive (curable) diluents that can be added to the polymer includeepoxy, vinyl ether, alcohol, acrylate and methacrylate monomers andoligomers. Such polymers and other diene-based polymers may also beadded or blended. Examples of epoxy reactive diluents includebis(2,3-epoxycyclopentyl)ether (Union Carbide EP-205), vinyl cyclohexenedioxide, limonene oxide, limonene dioxide, pinene oxide, epoxidizedfatty acids and oils like epoxidized soy and linseed oils.

The polymers may also be cured without the use of radiation by additionof a cationic initiator. Suitable initiators include the halides of tin,aluminum, zinc, boron, silicon, iron, titanium, magnesium and antimony,and the fluoroborates of many of these metals. BF complexes such asBF-ether and BF-amine are included. Also useful are strong Bronstedacids such as trifluoromethanesulfonic (triflic acid) and the salts oftriflic acid such as FC-520 (3M Company). The cationic initiator ischosen to be compatible with the polymer being crosslinked, the methodof application and cure temperature. The epoxy-containing polymers mayalso be crosslinked by the addition of multifunctional carboxylic acids,acid anhydrides, and alcohols, and in general by the curing methodsdescribed in U.S. Pat. No. 3,970,608, which is incorporated byreference. Volatile amines can be used to inhibit or retard unwantedcure, such as to maintain fluidity in one pack formulations until theyare applied and reach the appropriate bake temperature for cure.Radiation crosslinking is preferred because reactive ingredients do notcome in contact with warm adhesives.

The crosslinked materials of the present invention are useful inadhesives (including pressure sensitive adhesives, contact adhesives,laminating adhesives and assembly adhesives), sealants, coatings, films(such as those requiring heat and solvent resistance), printing plates,fibers, and as modifiers for polyesters, polyethers and polyamides. Thepolymers are also useful in asphalt modification. In addition to thefunctionalized polymer and any curing aids or agents, productsformulated to meet performance requirements for particular applicationsmay include various combinations of ingredients including adhesionpromoting or tackifying resins, plasticizers, fillers, solvents,stabilizers, etc. as descrivbed in detail in the aforementioned commonlyassigned applications which are incorporated by reference.

Compositions of the present invention are typically prepared by blendingthe components at an elevated temperature, preferably between 50° C. and200° C., until a homogeneous blend is obtained, usually less than three(3) hours. Various methods of blending are known to the art and anymethod that produces a homogeneous blend is satisfactory. The resultantcompositions may then preferably be used in a wide variety ofapplications. Alternatively, the ingredients may be blended into asolvent.

Adhesive compositions of the present invention may be utilized as manydifferent kinds of adhesives' for example, laminating adhesives,flexible packaging laminating adhesives, pressure sensitive adhesives,tie layers, hot melt adhesives, solvent borne adhesives and waterborneadhesives in which the water has been removed before curing. Theadhesive can consist of simply the epoxidized polymer or, more commonly,a formulated composition containing a significant portion of theepoxidized polymer along with other known adhesive compositioncomponents. A preferred method of application will be hot meltapplication at a temperature around or above 100° C. because hot meltapplication above 100° C. minimizes the presence of water and other lowmolecular weight inhibitors of cationic polymerization. The adhesive canbe heated before and after cure to further promote cure or post cure.Radiation .cUr.e of hot adhesive is believed to promote faster cure thanradiation cure at room temperature.

Preferred uses of the present formulation are the preparation ofpressure-sensitive adhesive tapes and the manufacture of labels. Thepressure-sensitive adhesive tape comprises a flexible backing sheet anda layer of the adhesive composition of the instant invention coated onone major surface of the backing sheet. The backing sheet may be aplastic film, paper or any other suitable material and the tape mayinclude various other layers or coatings, such as primers, releasecoatings and the like, which are used in the manufacture ofpressure-sensitive adhesive tapes. Alternatively, when the amount oftackifying resin is zero, the compositions of the present invention maybe used for adhesives that do not tear paper and molded goods and thelike.

Example 1

Polymer 1 was a symmetric star polymer (A-B-M_(o))₁₇ -X-C_(o) havingpolyisoprene A blocks and polybutadiene B blocks. It was prepared byanionic polymerization using two reactors. The polyisoprene block wascompletely polymerized in cyclohexane using sec-butyl lithium initiatorin the first reactor, then the polyisoprene solution was transferred tothe second reactor which contained additional cyclohexane and diethylether cosolvent and part of the butadiene monomer; additional butadienemonomer was added until the complete diblock polymer arm polymerizationwas complete. DVB-55 was added to couple the arms and after about anhour reaction time, methanol was added to terminate the living polymer.The diethyl ether cosolvent was incorporated to cause increased1,2-polymerization of the butadiene. The amounts of monomer used were29.82 pounds of 1,3-isoprene, 170.18 pounds of 1,3-butadiene and 17.19pounds of commercial divinylbenzene mixture (DVB-55 from Dow). Accordingto GPC analysis on the final polymer, about 83% of the arms were coupledby the DVB with 17% left unattached. The peak molecular weight of thepolyisoprene-polybutadiene arms (A-B arms) prior to coupling with theDVB was about 5780. Therefore, the molecular weights of the A and Bblocks were about 910 and 4870, respectively, and the molecular weightof that portion of the polyDVB associated with each of these arms wasabout 490, for a total of about 6270. The weight average molecularweight, M_(w), of the polymer was measured by static light scattering.Dry polymer was dissolved in tetrahydrofuran and filtered through a 0.5and a 0.2 micron filter. The analysis wavelength was 632.8 mn, thetemperature was 25.0° C. and the DRI was 0.146. The M_(w) determined was105,000. Dividing this M_(w) by 6270 indicates that the star polymer hadan average of about 17 diblock arms. Hence, for every mole of activeinitiator (sec-butyl lithium), about 13 moles of 1,3-isoprene, 90 molesof 1,3-butadiene and 3.8 moles of commercial divinylbenzene mixtures(DVB-55 from Dow) were polymerized; and n=17. The weight percentcomposition for the polymer is shown.

    ______________________________________                                        Polymer 1 composition                                                                        weight %                                                       ______________________________________                                        sec-butyl group  0.9                                                          polyisoprene     13.6                                                         polybutadiene    77.7                                                         DBV-55 mixture   7.8                                                          ______________________________________                                    

¹ H NMR analysis on the polymer indicated that the polyisoprene A blockscontained about 11% of their isoprene units in the 3,4-configuration(1,1-disubstituted ODB's) and about 89% in the 1,4-configuration(1,1,2-trisubstituted ODB's), and that the internal polybutadiene Bblocks contained about 40% of their butadiene units in the1,2-configuration (monosubstituted ODB's) and about 60% in the1,4-configuration (1,2-disubstituted ODB's). The correspondingconcentrations of mono-, di-, and trisubstituted olefinic double bondsin each block are shown below.

    ______________________________________                                                      Milliequivalents of olefinic double                                           bonds per gram of each block                                    Type            Block A     Block B                                           ______________________________________                                        monosubstituted ODB's                                                                         0           7.3                                               disubstituted ODB's                                                                           1.5         11.2                                              trisubstituted ODB's                                                                          12.3        0                                                 ______________________________________                                    

Example 2

Polymer 2: A portion of polymer 1 solution was epoxidized at 20° C. in astirred reactor flask using a solution of peracetic acid according tothe recipe below.

    ______________________________________                                        Epoxidation recipe:                                                           ______________________________________                                        polymer 1, g of solution                                                                          2506                                                      (polymer = 564 g, solvent                                                     mixture = 1942 g)                                                             sodium carbonate, g 4.50                                                      peracetic acid solution, g                                                                        208                                                       ______________________________________                                    

Peracetic acid (from FMC Corp.) typically consists of 35% peraceticacid, 39% acetic acid, 5% hydrogen peroxide, 1% sulfuric acid and 20%water, all by weight. The peracetic acid addition time was 35 minutes; a2 hour hold time followed. The 4.5 g of sodium carbonate was added intwo steps, half before the peracetic acid addition and the other 2.25 ghalfway into the peracetic acid addition. Sufficient sodium carbonate(122 g) to completely neutralize the peracetic acid solution wasdissolved in distilled water to give 6000 g of wash solution. Thissodium carbonate wash solution was added to another flask and theepoxidized polymer solution was added to it while stirring. The mixturewas stirred for 30 minutes, agitation was stopped and the bottomwater/sodium acetate layer was removed. The polymer solution was washedthree additional times with distilled water (3500 g each time). Thefinal wash water removed from the polymer solution had a pH of 5.9 andan electrical conductivity of 50 micromohs/cm. The polymer was recoveredby drying.

¹ H NMR analysis on the polymer before and after epoxidation gave thefollowing breakdown of the olefinic double bonds concentrations in thepolymers, the net change in the quantity of each type of ODB and amountof epoxide formed in the final polymer. The generation of 1.71 Meq/g ofepoxide causes a 2.74% weight increase (1.71*0.016*100%) from polymer 1to polymer 2.

    ______________________________________                                        .sup.1 H NMR Results, Meq/g Polymer                                                    Polymer  Polymer  Polymer 2                                                                              Change                                    Source   1        2        Values*1.027                                                                           P1-P2*1.027                               ______________________________________                                        1,4-     2.25     1.06     1.09     1.16                                      polyisoprene                                                                  3,4-     0.29     0.25     0.26     0.03                                      polyisoprene                                                                  1,4-     8.91     8.13     8.35     0.56                                      polybutadiene                                                                 1,2-     5.82     5.66     5.82     0.00                                      polybutadiene                                                                 epoxide  0.00     1.71     1.76     Total = 1.75                              ______________________________________                                    

The last column, above, shows the net change in each particular type ofolefinic double bond and its the basis for determining how much and whatkind of epoxides are present in the A and B blocks of polymer 2. TheMeq/g values in the last column indicate that 68% of the epoxidationoccurred in the polyisoprene A blocks and that 32% occurred in thepolybutadiene B blocks. Hence, the A blocks increased in molecularweight from 910 to 1030 and have 7.3 Meq of di- and trisubstitutedepoxide per gram of block, while the B blocks increased in molecularweight from 4870 to 4920 and have 0.72 Meq of disubstituted epoxide pergram of block B. The A:B ratio of epoxide is 10:1.

Although the polymer 2 is not an example of the present inventionbecause the molecular weights of the A and B blocks are small, thepolymers and procedures of Examples 1 and 2 clearly show how polymers ofthe present invention can be prepared. All that would need be done is toreduce the amount sec-butyl lithium initiator used in the preparation ofpolymer 1 to about one-fourth or less of the level that was used, asthis would cause the A and B molecular weights to fall above 3000 and15,000 respectively.

Example 3

Polymer 3 was a symmetric star polymer (A-B-M₁)₁₇ -X-C_(o) havingpolyisoprene A and M blocks and polybutadiene B blocks. It was preparedby anionic polymerization in cyclohexane. For every mole of activeinitiator (sec-butyl lithium), about 75 moles of 1,3-isoprene, 519 molesof 1,3=butadiene, 10 moles of 1,3-isoprene and 6 moles of commercialdivinylbenzene mixture (DVB-55 from Dow) were polymerized successively.A small amount of diethyl glyme was added to the polymer solution justbefore the addition of the butadiene monomer for the purpose ofpolymerizing the butadiene to a high 1,2-configuration. The polymer wasterminated with methanol. The molar ratios correspond to the given % byweight composition for the polymer. The peak molecular weight of thepolyisoprene-polybutadiene-oligoisoprene arms, A-B-M arms, prior tocoupling with the DVB, as measured by GPC, was about 33,000. Themolecular weights of the A, B and M blocks were about 5,000, 28,000 and700, respectively. About 84% of the arms were coupled. Based oncomposition, the A and the M blocks had about 14.7 Meq/g of residualODB's most of which were trisubstituted, while the B blocks had 18.5Meq/g of double bonds, none of which were trisubstituted. ¹ H NMRanalysis on the A-B and A-B-M segments prior to DVB coupling indicatedthat the external polyisoprene blocks, A, contained about 10% of theirisoprene mers in the 3,4 configuration and about 90% in the 1,4configuration, the internal polybutadiene blocks, B, contained about 81%of their butadiene mers in the 1,2 configuration and about 19% in the1,4 configuration, and the polyisoprene miniblocks, M, had about 36% oftheir mers in the 3,4 configuration and about 64% in the 1,4configuration. The concentrations of tri-, di- and monosubstitutedolefinic double bonds in each block are summarized below.

    ______________________________________                                        Polymer 3 composition                                                                        weight %                                                       ______________________________________                                        polyisoprene   14.7                                                           polybutadiene  81.0                                                           polyisoprene   2.0                                                            DVB mixture    2.3                                                            ______________________________________                                                     Milliequivalents of olefinic double                                           bonds per gram of each block                                     Type         Block A     Block M  Block B                                     ______________________________________                                        trisubstituted ODB                                                                         13.2        9.4      0                                           disubstituted ODB                                                                          1.5         5.3      3.5                                         monosubstituted ODB                                                                        0           0        15.0                                        ______________________________________                                    

Example 4

Polymer 4: Polymer 3 was partially hydrogenated using a nickel-aluminumcatalyst under conditions that do not hydrogenate aromatic double bondsand will preferentially hydrogenate olefinic double bonds that are notTU sites. The catalyst was washed out. The hydrogenation catalyst wasmade by the reaction of nickel 2-ethylhexanoate and triethylaluminum(AL/Ni ratio was about 2.3/1) and was used at 13 ppm nickel (18×10⁻³mmoles Ni/g polymer) on a solution basis, at a pressure of 500 psi and atemperature of about 70° C. The M_(w) was 585,000 as determined bystatic light scattering. The DRI was 0.096.

¹ H NMR analysis provided the following approximate composition of theresidual olefinic double bonds (ODB) in Polymer 4, as given below. Usingthese results, the ODB concentration in the A+M and the B blocks can becalculated. These values are also shown below. It is reasonable toassume that under the hydrogenation conditions both blocks A and Mhydrogenated about the same. Therefore it can be concluded that thetotal di- and trisubstituted ODB concentration reported for A+M isapproximately the same as that of the A blocks and of the M blocksindividually. In any event, the concentration range for the A blockscannot be more than about 2.9 to about 4.8 Meq/g, even if none or all ofthe isoprene mers in block M were hydrogenated, respectively. The.ratioof unsaturation in the A blocks to that in the B blocks was 5.5:1.Polymer 4 is an example of this invention.

    ______________________________________                                        .sup.1 H NMR results (Polymer 4)                                                                    Meq/g polymer                                           ______________________________________                                        1,4 polyisoprene (trisubstituted ODB)                                                               0.63                                                    3,4 polyisoprene (disubstituted ODB)                                                                0.08                                                    1,4 polyisoprene (disubstituted ODB)                                                                0.62                                                    1,2 polyisoprene (monosubstituted ODB)                                                              0.06                                                    Total                 1.39                                                    ______________________________________                                                Milliequivalents                                                              per gram of block                                                     Type      Block A + M Block B                                                 ______________________________________                                        trisubstituted                                                                          3.77        0                                                       disubstituted                                                                           0.48        0.77                                                    monosubstituted                                                                         0           0.07                                                    Total (di & tri-)                                                                       4.25        0.77     A/B ratio = 5.5                                ______________________________________                                    

Example 5

Polymer 5: Polymer 4 was epoxidized at 45° C. using a solution ofperacetic acid from FMC Corp. according to the recipe below, using astirred reactor flask, a 60 minute peracetic acid addition time and a 6hour hold. The sodium carbonate was added in two steps. After the 6 hourhold, sufficient sodium carbonate was added to neutralize all the aceticand any residual peracetic acid in the reaction flask, the polymersolution was thoroughly washed with water and the solvent was separatedfrom the polymer by drying.

    ______________________________________                                        Epoxidation                                                                   ______________________________________                                        polymer, g            275                                                     solvent (mostly cyclohexane), g                                                                     1762                                                    sodium carbonate, g   4.07                                                    peracetic acid solution, g                                                                          188                                                     ______________________________________                                    

¹ H NMR analysis on the polymer gave the following approximatebreak-down of residual olefinic double bonds left and the approximateamount of epoxide formed in the polymer.

    ______________________________________                                        .sup.1 H NMR results  Meq/g polymer 5                                         ______________________________________                                        1,4 polyisoprene (trisubstituted ODB)                                                               0.03                                                    3,4 polyisoprene (disubstituted ODB)                                                                0.01                                                    1,4 polyisoprene (disubstituted ODB)                                                                0.02                                                    1,2 polyisoprene (monosubstituted ODB)                                                              0.04                                                    Total ODB             0.10                                                    epoxy group           1.23                                                    Total ODB + epoxide   1.33                                                    ______________________________________                                    

The addition of 1.23 Meq epoxide/g polymer causes a 2% weight gain. Thetitrated value found for the amount of epoxide in Polymer 5 was about1.01 Meq/g.

The effect of the epoxidation of Polymer 4 was to epoxidize about 94% ofthe total di- and trisubstituted ODB on the polyisoprene blocks, A andM, and about 97% of disubstituted ODB on the polybutadiene blocks, B,and create epoxidized Polymer 5. Hence, for Polymer 5, the A and Mblocks each have about 4.0 Meq epoxide/g, and B blocks have about 0.75Meq epoxide/g. The ratio of epoxide in the A:B blocks was about 5.3:1.Polymer 5 is an example of the invention.

Example 6

Polymer 5 was used to make formulations A, B, C, and D. Formulation A isjust neat polymer with a small amount of antioxidant added whileformulation B included 25% of the tackifying resin Escorez® 5380(Exxon). These formulations were intended for EB curing. Formulations Cand D are similar to A and B respectively, except that 1% UVI-6974photoinitiator (Union Carbide) was added to facilitate UV cure. UVI-6974absorbs UV light from 188 to about 350 nm.

    ______________________________________                                        Formulation   A      B          C    D                                        ______________________________________                                        Polymer 5     99.7   74.8       98.7 74.0                                     Excorez ® 5380                                                                          0.0    24.9       0.0  24.7                                     UVI-6974      0.0    0.0        1.0  1.0                                      Irganox ® 1010                                                                          0.3    0.3        0.3  0.3                                      ______________________________________                                    

Formulations A and B were dissolved in toluene and cast onto sheets of 1mil Mylar to give about 3 mil layers of dry formulation after solventevaporation. Formulations C and D were dissolved in a 75/25 weight %mixture of toluene/n-butanol and similarly cast. Immediately beforeirradiating the film samples, the samples were preheated in an oven for2 minutes at 149° C. to remove any moisture and simulate having justbeen hot melt coated. EB irradiation was done on an ESI CB-150 processorusing 165 Kev electrons. UV irradiation was done on a Linde PS-2000Laboratory Photocure unit having a single medium pressure Hg bulbdelivering UV radiation from 188 nm to 365 nm, aluminum reflectors and avariable speed carrier belt. UV dose was controlled by varying theconveyor speed, which has a 60 fpm maximum and by inserting a filter.The filter prevents UV irradiation below about 300 nm from reaching thetest product. This reduces the incidence of UV energy that overlaps theabsorbance spectrum of the UVI-6974 photoinitiator by a factor of about4. For both EB and UV curing, a nitrogen blanket was used to suppressozone formation and its. consequent discharge into the workingenvironment. Curing involves a cationic mechanism which is known not tobe inhibited by oxygen. The formulations were tested for polymer gelcontent (solvent resistance) and other properties of a high performancePSA adhesive. The results are given in Table 1.

The results in Table 1 show that Polymer 5 can be cured to high gelcontents at low doses of EB or UV irradiation. In formulations A and B,the polymer was cured to over 80% gel with just 1 Mrad of EBirradiation. In formulations C and D, the polymer was fully cured with asingle pass under the unfiltered UV bulb at 20, 40, and 60 fpm, whichwas the maximum speed available on the UV processing unit. Even whenusing the filter to prevent UV light with a wavelength less than about300 nm from reaching the test specimen, formulation C was fully cured at20 fpm and formulation D was fully cured at 40 fpm. PSA testing offormulations C and D show that without curing the formulations lacksufficient cohesive strength to be useful as pressure sensitiveadhesives. However, PSA testing of the UV cured samples shows thatformulation C (the polymer) or, better yet, formulation D (thetackifying resin containing polymer) are excellent adhesives havingsufficient cohesive strength to allow good tack properties (rolling balltack and Polyken probe tack), and clean peeling (180° C. peel fromsteel) and provide high temperature shear resistance (95° C. holdingpower to Mylar).

                                      TABLE 1                                     __________________________________________________________________________    Electron Beam Cure                                                            % Polymer Gel Content                                                         Formulation                                                                   dose, Mrads           A B                                                     __________________________________________________________________________    0                      0                                                                               0                                                    1                     85                                                                              81                                                    2                     88                                                                              86                                                    __________________________________________________________________________                   95° C. Holding*                                                                Rolling                                                                           Polyken                                                                            180° Peel                                      Polymer Gel                                                                          Power to                                                                              Ball                                                                              Probe                                                                              from                                                  Content                                                                              Mylar   Tack                                                                              Tack steel                                         Formulation:                                                                          (%)    (minutes)                                                                             (cm)                                                                              (Kg) (pli)**                                       line speed, fmp.sup.1                                                                 C  D   C   D   C D C D  C   D                                         __________________________________________________________________________    UV Cure - no filter                                                           no cure  0  0    0   0 cohesive failure                                                                       1.7 2.7                                                      cohesive failure cohesive failure                              60      95 100 >1000                                                                             >1000                                                                             3 3 .8                                                                              .9 1.2 2.5                                       40      97 100 >1000                                                                             >1000                                                                             3 4 .6                                                                              .8 1.2 2.3                                       20      99 100 >1000                                                                             >1000                                                                             2 3 .6                                                                              1.2                                                                              1.0 2.1                                       __________________________________________________________________________    UV Cure With Use of a Filter                                                  60      86 95  >1000                                                                              500                                                                              1 4 .8                                                                              1.2                                                                              2.6 c                                                                             4.0 c                                     40      92 94  >1000                                                                             >1000                                                                             2 3 .6                                                                              .9 1.3 c                                                                             2.7                                       20      98 98  >1000                                                                             >1000                                                                             3 2 .6                                                                              1.0                                                                              0.9 2.1                                       __________________________________________________________________________     *1 square inch overlap with 1 Kg mass.                                        **pli = pounds per linear inch.                                               c = slight cohesive failure.                                             

I claim:
 1. A process for the production of a partially hydrogenatedconjugated diene block copolymer of the formula

    D.sub.n -X-C.sub.r

wherein D is A-B-M_(p) or (A-B)_(j) -M_(p) or A-(B-A)_(j) -M_(p) ; andwherein A is a diene block which has a molecular weight of 3,000 to50,000; and wherein B is a diene block which has a molecular weight offrom 15,000 to 200,000; and wherein C is a block or multiblock segmentwhich has a molecular weight of from 100 to 200,000 and comprises A, Bor methacrylate or mixtures thereof but is not identical to D; andwherein the B block may comprise up to 50% of a monoalkenyl aromatichydrocarbon monomer and the A blocks may comprise up to 99% of amonoalkenyl aromatic hydrocarbon monomer; and wherein M is a miniblockof a monomer selected from the group consisting of vinyl aromatichydrocarbons and dienes and which has a molecular weight of 50 to 3000;and wherein the A blocks contain a greater concentration of di-, tri-,or tetrasubstituted olefinic epoxides than the B blocks; and wherein Xis a coupling agent or coupling monomers or initiator, j is 1 to 6, n≧2,r≧0, n≧r, n+r ranges from 3 to 100 and p is 0 or 1;said processcomprising polymerizing the diene which makes up block A under anionicpolymerization conditions to form block A, adding the diene which makesup block B to the reaction mixture and polymerizing it to form block Bat one end of block A, subsequently coupling AB diblocks together byadding X to the reaction mixture to form a coupled block copolymer, andpartially hydrogenatinq the coupled block copolymer such that the ratioof olefinic double bonds in the A blocks to that in the B blocks is atleast 3:1.
 2. A process for the production of a partially hydrogenatedconjugated diolefin block copolymer of the formula

    (A-B).sub.k or A-(B-A).sub.j

wherein A is a diene block which has a molecular weight of 3000 to50,000; and wherein B is a diene block which has a molecular weight offrom 15,000 to 200,000; and wherein the A blocks contain a greaterconcentration of di-, tri-, or tetrasubstituted olefinic epoxides thanthe B blocks; and wherein j is 1 to 6 and k is 2 to 6; and said processcomprising polymerizing the diene which makes up block A under anionicpolymerization conditions to form block A, adding the diene which makesup block B to the reaction mixture and polymerizing it under anionicpolymerization conditions to form block B at one end of block A,optionally, repeating the sequential addition of said dienes and anionicpolymerization of them to form additional blocks to provide the blockcopolymer, and partially hydrogenating the block copolymer such that theratio of olefinic double bonds in the A blocks to that in the B blocksis at least 3:1.